Basically three lenses for each district with a regional bonus: Industrial Zones, Entertainment Districts and Water Parks. (that's all, I think?)

Color 1: Highlights those districts of the chosen type that have their respective regional bonus building (factories etc.) in one color.

Color 2: Districts of the chosen type without those buildings.

Color 3: Highlights all the hexes that are in range of a regional bonus.

Color 4: Highlights the city centers that already receive the bonus.

Color 5: Highlights the city centers without a bonus.

would save so much time (vent on) I'M SICK OF MANUALLY COUNTING HEXES AND LOOKING AT TOOLTIPS TO CONFIRM BONUS! (vent off)

optionally: add to a tooltip in settler lens info about building bonuses that reach a specific hex